This invention relates generally to circuit interrupters, and more particularly to a high voltage circuit interrupter which uses a projection on a rotatable movable impedance contact to provide a non-uniform electric field distribution when the impedance contacts are moving toward the closed position.
It is known that high voltage surges, depending upon circuit conditions, can occur during the closing of the contacts of a high voltage circuit interrupter. One method of reducing the lever of such high switching surges is described in U.S. Pat. No. 3,291,947, where a resistance is inserted into the circuits of the circuit interrupter prior to the time of engagement between the main contacts. U.S. Pat. No. 4,072,836 also discloses the use of a resistor inserted into the circuit during the closing operation of a high voltage circuit interrupter.
When interrupting very high voltages, for example 500 kV, it is not uncommon to utilize two or more individual interrupting heads serially connected to provide the necessary interrupting distances. This use of multiple interrupting heads can cause coordination problems, particularly with respect to closing on an energized transmission line. This is particularly critical for the insertion of the resistors into the circuit. For correct operation of the resistor insertion scheme, it is essential that the impedance contacts within all the interrupting units close within a couple of microseconds. In practice, the gaps between the impedance contacts can be mechanically aligned this closely only with great difficulty, and sparking and breakdown between other gaps is not unusual. Thus, it would be desirable to eliminate the necessity of such a precise interconnection between the resistor insertion contacts without increasing the probability of sparking and breakdown.